# openfang-rail

> Deterministic business-identifier validation (IBAN, LEI, VAT, UK company number) and rental due-diligence (deposit-safety, listing-risk, one signed verdict), paid per call via x402 (gasless EIP-3009 USDC on Base). Zero custody, signed receipts, offline + explainable (no ML, no scraping). First 20 calls/day free.

## For agents
- Discover: GET /.well-known/mcp.json and /.well-known/x402.json
- MCP: POST /mcp (JSON-RPC 2.0: initialize, tools/list, tools/call)
- REST: POST /v1/tools/{tool}/call with body {"input":{ … }} (see each tool's input_schema in mcp.json)
- Free tier first; then a 402 challenge — sign an EIP-3009 voucher, retry with X-PAYMENT.
- Every result carries a signed XDR-1 receipt; recover the signer to verify offline.

## Tools
- iban-check: Validate an IBAN by ISO 13616 structure and MOD-97-10 checksum (offline, no bank lookup).
- lei-check: Validate a Legal Entity Identifier (ISO 17442 + ISO 7064 MOD-97-10 check digits).
- vat-mod97-check: Structural VAT check (BE mod-97 family).
- company-number-format: Validate UK Companies House number format (not existence).
- rent-deposit-guard: Rental deposit safety: IBAN checksum + property/deposit country alignment + pre-viewing flag.
- rental-listing-risk: Explainable rental-fraud risk score over listing red-flag signals (deterministic rule engine).
- rental-verdict: One combined, signed rental due-diligence verdict: deposit + landlord entity (LEI/company) + listing risk.

Price 0.00059 USDC/call. Non-custodial; payer->seller direct on Base.